Examples

HelloWorld example

In this example, we will try to define a basic service using proto buffers, register it using the service client and calling it by its route.

Proto file definition:

helloworld.proto

syntax="proto3";

package my.package.v1;

service HelloWorld {
	rpc addOne(Request) returns (Response) {}
}

message Request {
	int32 value = 1;
}

message Response {
	int32 value = 1;
}

Callee (server):

callee.js

const path = require('path')

const { ServiceClient } = require('hera-grpc')

const sc = new ServiceClient({
	host: 'localhost',
	port: 50051,
	zk: 'zk://localhost:2181/hera-test',
})

sc.registerService({
	routes: '/example-1.0.0/dev~service_route/helloworld',
	serviceName: 'my.package.v1.HelloWorld',
	filename: path.join(__dirname, 'helloworld.proto'),
	handlers: {
		addOne: (call, callback) => {
			const { request } = call
			callback(null, { value: request.value + 1 })
		},
	},
})

sc.on('error', (error) => {
	console.error('Error from service client:', error)
})

try {
	sc.connect()
} catch (error) {
	console.error('Callee error:', error)
	sc.close()
}

this will register the HelloWorld service for route /example-1.0.0/dev~service_route/helloworld and start the grpc server on localhost:50051.

Registered event

The service client will emit registered event when it's ready to handle requests - for more details check events.

Caller (client):

Client can now call the service by its route /example-1.0.0/dev~service_route/helloworld:

caller.js

const { assert } = require('console')
const promisify = require('util').promisify

const { ServiceClient } = require('hera-grpc')

const sc = new ServiceClient({
	zk: 'zk://localhost:2181/hera-test',
})

sc.once('connected', async () => {
	// Get stub with the rpc methods for the specified route
	const stub = await sc.getStub('/example-1.0.0/dev~service_route/helloworld')
	stub.addOne = promisify(stub.addOne)

	const request = { value: 41 }
	const response = await stub.addOne(request)

	assert(response.value === 42)

	stub.close()
	sc.close()
})

sc.once('error', (error) => {
	process.exitCode = 1
	console.error('Error from service client:', error)
	sc.close()
})

try {
	sc.connect()
} catch (error) {
	console.error('Caller error:', error)
	sc.close()
}

POI service example

In this example, we will try to register and call the demo service from the Node gRPC Basics tutorial:

Callee (server):

callee.js

const path = require('path')

const { ServiceClient } = require('hera-grpc')

const poiProtoPath = path.join(__dirname, '../proto/poi/poi.proto')

// Handlers from the POI service tutorial
const poiHandlers = require('./poi/handlers')

const sc = new ServiceClient({
	host: 'localhost',
	port: 50051,
	zk: 'zk://localhost:2181/hera-test',
})

sc.registerService({
	routes: '/example-1.0.0/dev~service_route/poi',
	serviceName: 'RouteGuide',
	handlers: poiHandlers,
	filename: poiProtoPath,
	loadOptions: {
		keepCase: true,
		longs: String,
		enums: String,
		defaults: true,
		oneofs: true,
	},
})

sc.on('error', (error) => {
	console.error('Error from service client:', error)
})

try {
	sc.connect()
} catch (error) {
	console.error('Callee error:', error)
	sc.close()
}

this will register the poi service for route /example-1.0.0/dev~service_route/poi.

Caller (client):

caller.js

const { ServiceClient } = require('hera-grpc')

const poiClient = require('./poi/client')

const sc = new ServiceClient({
	zk: 'zk://localhost:2181/hera-test',
})

sc.once('connected', async () => {
	// Get stub with the rpc methods for the specified route
	const stub = await sc.getStub('/example-1.0.0/dev~service_route/poi')

	// Client from the tutorial
	await poiClient(stub)

	stub.close()
	sc.close()
})

sc.once('error', (error) => {
	process.exitCode = 1
	console.error('Error from service client:', error)
	sc.close()
})

try {
	sc.connect()
} catch (error) {
	console.error('Caller error:', error)
	sc.close()
}